From BlenderWiki

Preparing

• The first step when using Grease Pencil is to enable the display of Grease Pencil drawings. To do this, locate the Grease Pencil entry on the tool shelf (T if not open) and on the properties panel (N if not open).
• At this point, click on New Layer to add a new layer to draw on. This step is not necessary when you are starting off a new drawing (as a new layer will automatically be created for you), unless you want to customize the line width, color, or opacity before drawing. However, if you want to draw on a new layer once layers already exist, it is necessary to click on the button.

Grease Pencil is available for the following editor (window) types: 3D View and UV/Image Editor.

Draw a stroke

Description

Draw a new stroke (multiple short, connected lines). The stroke will finish when you release the mouse button.

Hints

While holding D, simply LMB and release to make a dot.

Draw a line

Description

Draw a new line in rubber band mode. The line will finish when you release the mouse button.

Erase stroke(s)

Description

Erases segments of strokes that fall within the radius of the eraser “brush”. The erasing will continue until the mouse button is released.

Options

The radius of the eraser “brush” is set under User Preferences » Editing » Grease Pencil » Eraser Radius.

Hints

If begun with Erase, either RMB or LMB will erase strokes.

Sketching Sessions

Description

A Sketching Session allows for the rapid sketching with grease pencil when multiple strokes are desired. With this option set, when a grease pencil stroke is made a sketching session starts. Now, each time LMB is pressed, a new stroke of the same type is begun. Use either Esc or ↵ Enter to exit the sketching session.

Hints

Either LMB or RMB is recognized for erasure.

Shared Grease Pencil Settings

Drawing Settings

At Transform Panel » Grease Pencil » Drawing Settings, there are up to four choices for drawing settings. These settings may be mixed within a grease pencil layer.

• View - New strokes are locked to the view. These strokes are not in 3D-space, but may be thought of as being drawn on the screen.
• Cursor (3D view only) - New strokes are drawn in 3D-space, with the position of their points being determined by the position of the 3D-cursor and the view rotation at the time (i.e. they are on the plane orthogonal to the view direction, and passing through the 3D cursor).
• Surface (3D view only) - New strokes are drawn in 3D-space, with their position being determined by the first visible surface "under" the stroke in the current view (i.e. they are projected onto said surface).
• Stroke (3D view only) - New strokes are drawn in 3D-space, with the position of their points being determined by the position of existing strokes in 3D-space which appear to be "under" the stroke in the current view (i.e. they are projected onto existing strokes). Note that strokes created with View are not in 3D-space and are not considered for this projection.

When using Surface or Stroke settings, if no part of a new stroke "lands" on a surface or existing stroke, the stroke does not appear to be saved. If some part of a new stroke does "land," then all of the new stroke is saved.

Checking Transform Panel » Grease Pencil » Drawing Settings » Only Endpoints applies the drawing setting only to the endpoints; strokes between are adjusted to lie on a plane passing through the endpoints.

Limitations

Cursor is available in the UV/Image Editor but it appears to function as View -- which it reverts to on ending the stroke.

Sensitivity When Drawing

The default settings for the sensitivity to mouse/stylus movement when drawing, have been set so that there shouldn’t be too much jitter while still allowing for fine details to be made. However, sometimes these settings may not be appropriate, in which case, the defaults can be found at User Preferences window » Editing » Grease Pencil.

• Manhattan Distance: The minimum number of pixels the mouse should have moved either horizontally or vertically before the movement is recorded. Decreasing this should work better for curvy lines.
• Euclidean Distance: The minimum distance that mouse should have traveled before movement is recorded. Imagine this as length of imaginary string between last recorded position and mouse-cursor.
• Eraser Radius: This is self-explanatory. It is simply the size of the eraser “brush”, so changing this will affect how likely strokes are going to be covered within the eraser brush and thus erased.
• Smooth Stroke: This turns on the post-processing step of smoothing the stroke to remove jitter. It is only relevant when not drawing straight lines. By default this is on. It should be noted that it can often cause “shrinking” of drawings, and may be turned off if the results are not desirable.

For Tablet Users

• The thickness of a stroke at a particular point is affected by the pressure used when drawing that part of the stroke.
• The “eraser” end of the stylus can be used to erase strokes too.

Drawing Planes

---

Additional 2.5x Information

as a note for those that will edit the page for real, I'm putting here this video,